BIke has no power and feels like its stalling!!

Well couple of days i got a new CNS carbi on my bike and i went for a test run and well it goes fast very fast so i went for a couple long rides and then one time wen i got my out to ride agen it seem to start fine b ut wudnt accelerate very fast i thought it was the carbi but it isnt and then it progressively got worse and now it feels like it cant pull anything and kinda feels like its stallling, but it kinda goes but only at like 20kmh on a slight downhill. I have also looked for clutch slipage no clutch slilpage. And while i had the clutch cover/casing off i had a look at the seal or wutever it is behind the small cog beside the big cog conneced to the clutch, from wut i see i think its come loose or broken and looks like its rubber, i was wondering if this was my problem?

if that seal came out or got damaged it could be your problem. with that seal damaged your engine will get to much air and have a lean condition. DO NOT RUN IT until you know for sure that the seal is ok. you may have already ran it to much and hurt the cylinder/piston.